Phylum Chordata Rank Species | Scientific name Gobiomorphus cotidianus Higher classification Gobiomorphus Order Perciformes | |
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Similar Gobiomorphus, Redfin bully, Giant bully, New Zealand smelt, Upland bully | ||
Facebook common bully
The common bully (Gobiomorphus cotidianus) is endemic to New Zealand, a freshwater fish present throughout the country. There are three other bully species that can be confused with common bullies. Few characteristis in the common bully separate it from the other species. Vertical lines present on the cheek are a good defining characteristic along with the location of head pores and scale patterns on the head although these characteristics are hard to establish when seen in the wild. It is a amphidromous fish meaning it is able to survive in marine and fresh water environments. It is a small fish only growing as big as 15 cm. It can live in marine, fresh water or brackish water (fresh and salt water mixed) habitats and generally lives in benthic zones. Some populations venture into the sea and occur in coastal rivers and streams while other land locked populations have established in many shallow mainland lakes. They generally prefer moderate to slow moving water which means they are the most likely bully species to be sighted. Its diet consists mainly of small benthic invertabrates but also involves insect larvae and crustacea.
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Natural history
Apart from few sightings in Stewart Island and Great Barrier Island, the common bully is found in mainland areas. These populations have established in land locked areas due to natural processes. It is thought that these populations of fish inhabited lakes or relatively high in river systems which were eventually blocked off from the sea due to natural processes. In these landlocked environments the common bully is an important prey for larger freahwater fish such as eels and trout.
Reproduction
In the summer months Gobiomorphus cotidianus can be found moving more into the littoral zones of the lakes and streams as the females prepare to reproduce. The femalels attach clusters of a several hundred to a few thousand eggs onto the underside of hard surfaces on the lake bottom where they are fertilized and guarded by the males. The larval stage of bullies are planktonic and their main source of food are zoo plankton. As the young grow larger they move into deeper habitats and become benthic once they reach about 18mm in length. They mature at around 1 year old and the average generation gap is 2 years.
